1. Field of the Invention
The present invention generally relates to antennas and more particularly to an antenna system having a requirement of operating over two or more separate frequency bands.
2. Description of the Prior Art
A first option in achieving an antenna operable over two frequency bands is to make the antenna frequency response broadband to cover both desired bands of operation. Quite often this technique is difficult to achieve due to compromises that must be made in the antenna impedance match and gain to achieve the desired bandwidth. The second option is to use two antennas fed by a diplexer which is useful when the required bands of operation are widely separated. This option yields a much larger overall antenna structure. In addition the diplexer has an insertion loss that lowers the effective gain of each antenna in the structure. There is also a potential problem of coupling between the antennas causing degraded performance.